Cat scratch disease (CSD) has been the subject of considerable clinical and microbiologic interest for many years. An estimated 7,000 cases of cat scratch disease occur each year in the United States. Due to difficulty in diagnosing CSD and its potentially confusing clinical similarity with other disease syndromes, the number of actual cases of CSD in the United States may be closer to 70,000 per year. CSD is described as a subacute regional lymphadenitis temporally associated with the scratch or bite of a cat, and it occasionally results in meningoencephalitis.
Diagnosis of CSD has been a problem because the etiologic agent of the disease has not been previously identified. An unidentified bacillus has been visualized in biopsies from patients with CSD using Warthin-Starry stain but has resisted identification because of difficulties in obtaining an isolated culture. The etiologic agent of CSD has recently been proposed to be "Afipia felis" (Brenner et al., J. Clin. Microbiol. 29:2450-60, 1991). Despite these efforts, it has not been possible thus far to isolate or otherwise associate this agent with most persons suffering from cat scratch disease.
A clinically related disease, bacillary angiomatosis (BA), is a condition characterized by multiple tumors or swelling due to proliferation of the blood vessels. BA is often found in association with an immunocompromised condition, particularly HIV infection. An unidentified bacillus has been visualized in the angiomatous tissues using Warthin-Starry stain (Relman et al., N. Eng. J. Med. 323:1573-80, 1990). DNA extracted from the angiomatous tissues was shown to contain a fragment of 16S rRNA gene related to, but not identical to, the 16S rRNA gene of Rochalimaea quintana. This DNA was not obtained from a pure culture of the organism (Relman et al. 1990). These investigators were unable to isolate an infectious organism from patient tissues and, therefore, were unable to clearly associate the DNA sequences observed in tissues with an identifiable disease-causing organism. Neither the organism seen in these tissues nor the actual causative agent of the disease was identifiable.
Thus, despite intensive research and widespread effects of the diseases, the etiologic agent(s) of both CSD and BA have evaded identification. This invention describes the identification of an organism, named R. henselae herein, which is causative of both diseases.